package com.processmining.util;

import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.impl.JsonWriteContext;
import org.codehaus.jackson.map.JsonSerializer;
import org.codehaus.jackson.map.SerializerProvider;
import org.codehaus.jackson.util.CharTypes;

public class StringUnicodeSerializer extends JsonSerializer<String> {
 private final char[] HEX_CHARS = "0123456789ABCDEF".toCharArray();
 private final int[] ESCAPE_CODES = CharTypes.get7BitOutputEscapes();
 private void writeUnicodeEscape(JsonGenerator gen, char c) throws IOException {
  gen.writeRaw('\\');
  gen.writeRaw('u');
  gen.writeRaw(HEX_CHARS[(c >> 12) & 0xF]);
  gen.writeRaw(HEX_CHARS[(c >> 8) & 0xF]);
  gen.writeRaw(HEX_CHARS[(c >> 4) & 0xF]);
  gen.writeRaw(HEX_CHARS[c & 0xF]);
 }
 private void writeShortEscape(JsonGenerator gen, char c) throws IOException {
  gen.writeRaw('\\');
  gen.writeRaw(c);
 }
 @Override
 public void serialize(String str, JsonGenerator gen,
   SerializerProvider provider) throws IOException,
   JsonProcessingException {
  int status = ((JsonWriteContext) gen.getOutputContext()).writeValue();
     switch (status) {
       case JsonWriteContext.STATUS_OK_AFTER_COLON:
         gen.writeRaw(':');
         break;
       case JsonWriteContext.STATUS_OK_AFTER_COMMA:
         gen.writeRaw(',');
         break;
       case JsonWriteContext.STATUS_EXPECT_NAME:
         throw new JsonGenerationException("Can not write string value here");
     }
     gen.writeRaw('"');//写入JSON中字符串的开头引号
     for (char c : str.toCharArray()) {
       if (c >= 0x80){
        writeUnicodeEscape(gen, c); // 为所有非ASCII字符生成转义的unicode字符
       }else {
         // 为ASCII字符中前128个字符使用转义的unicode字符
         int code = (c < ESCAPE_CODES.length ? ESCAPE_CODES[c] : 0);
         if (code == 0){
          gen.writeRaw(c); // 此处不用转义
         }else if (code < 0){
          writeUnicodeEscape(gen, (char) (-code - 1)); // 通用转义字符
         }else {
          writeShortEscape(gen, (char) code); // 短转义字符 (\n \t ...)
         }
       }
     }
     gen.writeRaw('"');//写入JSON中字符串的结束引号
 }
}